Quaternary bisphenolates, methods for their preparation, and uses thereof

ABSTRACT

Quaternary salts having a double helix structure are prepared by the reaction of dihydroxyaromatic compound, preferably a bisphenol, with an alkali metal hydroxide and a quaternary salt, such as a tetraalkylammonium or hexaalkylguanidinium chloride. The quaternary salts and their alkaline hydrolysis products are useful as catalysts in various reactions, including imide formation from bisphenol salts and halo- or nitro-substituted phthalimides and redistribution and equilibration of polycarbonates.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of application Ser. No. 08/768,871, filedDec. 17, 1996, now U.S. Pat. No. 5,756,843 which is hereby incorporatedby reference in its entirety. This application claims priority fromcopending provisional application Ser. No. 60/021,750, filed Jul. 15,1996.

BACKGROUND OF THE INVENTION

This invention relates to bisphenol chemistry, and more particularly tothe preparation of a genus of catalysts containing bisphenol moieties.

The use of tetraalkylammonium and hexaalkylguanidinium salts as phasetransfer catalysts in the preparation of various polymers is known. Inparticular, U.S. Pat. Nos. 4,273,712 and 5,132,423 disclose the reactionof bisphenol salts with halo- or nitro-substituted phthalimides in anorganic medium to produce bisimides which, upon conversion todianhydrides and reaction with diamines, form polyetherimides. U.S. Pat.Nos. 3,787,364, 3,838,097, 3,847,869 and 5,229,482 disclose a similarlyphase transfer catalyzed reaction of bisphenol salts with halo- ornitro-substituted bis(phthalimido) derivatives of aromatic diamines orwith similar compounds, resulting in the direct formation ofpolyetherimides and other polyether polymers. The phase transfercatalysts employed according to U.S. Pat. Nos. 5,132,423 and 5,229,482are guanidinium and especially hexaalkylguanidinium salts; in the otherpatents, tetraalkylammonium salts are disclosed as suitable catalysts.

The hexaalkylguanidinium salts which are easiest to prepare are thechlorides, but they are hygroscopic. It is burdensome to store them inanhydrous form and subsequently dry them or to isolate them in anhydrousform, which is essential for the polyetherimide-forming reactions.

One of the by-products in the reaction of bisphenol salts withnitro-substituted compounds is an alkali metal nitrite, typically sodiumnitrite. It is ordinarily removed by washing the organic reaction systemwith water. It would be desirable to recover the sodium nitrite and sellit for further use.

However, chloride levels in by-product nitrite salts are high, which cancause corrosion of metal reaction vessels in contact therewith. Inaddition, commercial applicability requires that sodium nitrite containa very low chloride level, typically no greater than 100 ppm by weight,which is difficult or impossible to attain with the use of ahexaalkylguanidinium chloride, for example, as a phase transfercatalyst.

For these reasons and others, it is desirable to prepare non-hygroscopichexaalkylguanidinium and tetraalkylammonium salts, as well as saltscontaining an anion other than chloride.

SUMMARY OF THE INVENTION

The present invention is based on the discovery of a novel series ofhydrogen-bonded tetraalkylammonium, tetraalkylphosphonium andhexaalkylguanidinium bisphenolates. These compounds are easilysynthesized or may be obtained from waste streams generated in variousstages of polyetherimide production. They can be obtained in high yieldby certain adjustments in the treatment of the waste stream.

The quaternary bisphenolates have high oxidative and thermal stabilityand are non-hygroscopic. Therefore, they are easily stored. They areconvertible to compounds effective as phase transfer catalysts in theproduction of polyetherimides and similar polymers. They are alsocapable of use in other processes involving the recycle of suchmaterials as hexaalkylguanidinium salts and bisphenols. Moreover, theythemselves are active as catalysts in the production of other polymersincluding linear and branched polycarbonates.

In one of its aspects, the invention includes quaternary salts ofdihydroxyaromatic compounds, said salts having the molecular formula

    H.sub.3 Q(OA.sup.1 O).sub.2,                               (I)

wherein A¹ is a divalent aromatic radical and Q is a monocationiccarbon- and nitrogen- or phosphorus-containing moiety.

Another aspect of the invention is a method for preparing a quaternarysalt of the type represented by formula I which comprises contacting adihydroxyaromatic compound of the formula (HO)₂ A¹ with an alkali metalhydroxide and a quaternary salt of the formula Q⁺ X⁻, wherein A¹, Q andY are as previously defined and X is halide.

Another aspect is a method for preparing a polyether or intermediatetherefor which comprises contacting, at a temperature in the range ofabout 100-250° C., at least one alkali metal salt of a dihydroxyaromaticcompound with at least one halo- or nitro-substituted aromatic compoundin the presence of a catalytic amount of an alkaline hydrolysis productof said quaternary salt of the type represented by formula I.

A further aspect is a method of preparing a branched polycarbonate whichcomprises equilibrating a reaction system comprising a linear orbranched polycarbonate of a different molecular weight from the desiredone in the presence of a polyphenolic compound and a catalytic amount ofsaid quaternary salt of the type represented by formula I.

Still another aspect is a method of preparing a polycarbonate whichcomprises contacting at least one dihydroxyaromatic compound with adiaryl carbonate in the melt in the presence of a catalytic amount ofsaid quaternary salt of the type represented by formula I.

DETAILED DESCRIPTION PREFERRED EMBODIMENTS

The Q radical in the quaternary salts of formula I is a monocationiccarbon- and nitrogen- or phosphorus-containing moiety; i.e., a moietyhaving a single positive charge. It may be a tetraalkylammonium ortetraalkylphosphonium moiety wherein the alkyl groups contain 2-12 andpreferably 2-6 carbon atoms, as illustrated by tetraethylammonium,tetra-n-butylammonium, tetra-n-butylphosphonium anddiethyldi-n-butylammonium. Preferably, however, it is ahexaalkylguanidinium moiety such as hexaethylguanidinium,hexa-n-butylguanidinium or tetraethyldi-n-butylguanidinium. The atomcontent of the Q radical is preferably 9-40 atoms including carbon andnitrogen or phosphorus atoms; its size is governed by the fact that thetetraethylammonium and tetraethylphosphonium cations contain 8 carbonatoms and one nitrogen or phosphorus atom for a total of 9, while thehexahexylguanidinium cation contains 37 carbon atoms and 3 nitrogenatoms for a total of 40.

The A¹ radical may be a monocyclic radical; i.e., an unsubstituted orsubstituted m- or p-phenylene radical. Most often, however, it has theformula

    --A.sup.2 --Y--A.sup.2 --,                                 (II)

wherein A² is unsubstituted p-phenylene and Y is a single bond or abridging radical wherein 1-2 atoms separate the A² values; i.e., A¹ is abisphenol-derived moiety. The preferred moieties of this type are thosein which A² is p-phenylene and Y may be any bridging radical in whichone or two atoms separate the two A² values. Illustrative Y radicalsinclude methylene, ethylene, isopropylidene, 2,2-dichloroethylidene,oxygen and sulfur. It is also possible for Y to be a single bond, as isthe case with 4,4'-biphenol. The preferred Y value is isopropylidene,which is present when the bisphenol employed as described hereinafter is2,2-bis(4-hydroxyphenyl)propane; i.e., bisphenol A.

By reason of the strong preference herein for compounds in which A¹ hasformula II, the quaternary salts of this invention are frequentlydesignated "quaternary bisphenolates" hereinafter. It should beunderstood, however, that quaternary salts wherein A¹ is monocyclic maybe substituted for quaternary bisphenolates where appropriate.

The quaternary salts of the invention may be prepared by the reaction ofa dihydroxyaromatic compound of the formula (HO)₂ A¹ with an alkalimetal hydroxide and a quaternary salt of the formula Q⁺ X⁻. The X valuein the quaternary salt is halide, preferably bromide or chloride andmost preferably chloride. Typical reaction temperatures are in the rangeof about 10-125° and preferably about 10-50° C. An inert atmosphere suchas nitrogen or argon may be employed.

In a preferred embodiment of the invention, the reaction takes place inan aqueous medium, most often also containing a C₁₋₃ alkanol andpreferably methanol. The quaternary bisphenolate is usually insoluble inwater but soluble in the alkanol, and often precipitates spontaneously;if not, it can be precipitated by addition of water.

It is generally found convenient to initially form an alcoholic mixtureof bisphenol and alkali metal hydroxide, whereupon the bisphenoldissolves as the alkali metal salt, and to add thereto anaqueous-alcoholic solution of the quaternary salt. Another alternativeis to combine the bisphenol and quaternary salt and gradually addaqueous alkali metal hydroxide solution thereto. In the water-alkanolembodiment, ambient temperatures in the range of about 20-30° C. aregenerally preferred.

In still another procedure, a non-polar organic solvent such as tolueneis employed. An aqueous alkaline solution of the quaternary salt isadded gradually to a combination of the bisphenol and refluxing solvent.The product precipitates out and can be purified by washing with water.Further purification of product obtained by any of these methods can beachieved by recrystallization, most often from an alkanol and preferablymethanol.

Reactant proportions are not critical in the method for preparing thequaternary bisphenolates. This is apparent from the fact that theirformation was initially discovered in mixtures comprising thenon-stoichiometric proportions of 2 moles of alkali metal hydroxide, 2moles of hexaalkylguanidinium chloride and 1 mole of bisphenol. Foroptimum yield, however, a bisphenol:quaternary salt:alkali metalhydroxide molar ratio of 2:1:0.5-1.5 and especially 2:1:1 is preferred.

X-ray diffraction analysis of the product obtained from bisphenol A,hexaethylguanidinium chloride and sodium hydroxide has shown it to havethe molecular structure of a double helix of anionic bisphenol Amoieties interconnected via hydrogen bonds between two oxygen atomsthrough the three protons. The hexaethylguanidinium cationic moietiesare ionically associated with the anionic double helix and most oftenare located within the pockets formed by the hydrogen bonds. A similarstructure is postulated for other quaternary bisphenolates of theinvention.

The preparation of the quaternary bisphenolates of this invention isillustrated by the following examples. All percentages are by weight."Catalyst solution" in these examples is, unless otherwise indicated, anaqueous solution of 28.54% hexaethylguanidinium chloride and 10.09%sodium chloride.

EXAMPLE 1

A 5-l round-bottomed flask was purged with nitrogen and charged with228.29 g (1 mole) of bisphenol A, 20.29 g (0.5 mole) of sodium hydroxideand 300 ml of methanol. The resulting solution was magnetically stirredunder nitrogen. A blend of 462.26 g of catalyst solution (0.5 mole ofhexaethylguanidinium chloride) and about 175 ml of methanol was addedrapidly, whereupon a solid immediately precipitated. Methanol, 900 ml,was added with stirring to redissolve all of the solids.

Stirring was continued for 15 minutes, after which 1100 ml of water wasadded to reprecipitate the solids. The flask was cooled to 20° C. in iceand vacuum filtered. The filter cake was washed with 1200 ml of waterand dried in a vacuum oven at 75° C., yielding 335.44 g (98.1% crudeyield) of a white solid. Recrystallization from methanol followed byvacuum drying yielded 244.14 g (71.4% of theoretical) of purifiedproduct in the form of colorless crystals with a melting point of208-210° C. The purified product was shown by elemental analysis, atomicadsorption analysis and proton nuclear magnetic resonance spectroscopyto be the desired hexaethylguanidinium bisphenolate, having thestoichiometric proportions of three hydrogen atoms, onehexaethylguanidinium cation moiety and two bisphenol A dianion moieties.

EXAMPLE 2

A 2-l jacketed reactor was charged with 228.29 g (1 mole) of bisphenol Aand catalyst solution equivalent to 0.5 mole of hexaethylguanidiniumchloride. The solution was mechanically stirred and heated to 90° C.,whereupon two liquid phases formed. Sodium hydroxide, 0.5 mole as anapproximately 15% aqueous solution, was added dropwise, whereupon awhite precipitate formed. Water, 500 ml, was added and stirring wascontinued for about 15 minutes. Upon workup as in Example 1, the desiredhexaethylguanidinium bisphenolate was obtained in 98.3% crude and 69.2%pure yield.

EXAMPLE 3

A 500-ml, 3-necked round-bottomed flask was charged with 22.8 g (100mmol) of bisphenol A and 250 ml of toluene. The flask was fitted with aDean-Stark trap and an addition funnel and the resulting solutiontherein was heated to reflux, with stirring. The addition funnel wascharged with catalyst solution equivalent to 50 mmolhexaethylguanidinium chloride and with 50% aqueous sodium hydroxidesolution containing 4.00 g (50 mmol) of sodium hydroxide, and thiscombination was added dropwise to the refluxing bisphenol A solution.The funnel was washed with 100 ml of water which was then added to theflask, after which the water was removed by azeotropic distillationcausing precipitation of a white solid. The contents of the flask werefiltered and the filter cake was washed with 600 ml of water and driedin a vacuum oven. The crude yield of the desired hexaethylguanidiniumbisphenolate was 33.1 g, or 96.7% of theoretical.

EXAMPLE 4

The procedure of Example 1 was repeated, substitutingbis(4-hydroxyphenyl) sulfide on an equimolar basis for the bisphenol A.A similar product, melting at 158-160° C., was obtained.

EXAMPLE 5

The procedure of Example 1 was repeated, substituting1,1-dichloro-2,2-bis(4-hydroxyphenyl)ethylene on an equimolar basis forthe bisphenol A. A similar product, melting at 178-180° C., wasobtained.

EXAMPLE 6

The procedure of Example 1 was repeated, substitutinghexa-n-propylguanidinium chloride on an equimolar basis for thehexaethylguanidinium chloride. A similar product, melting at 209-211°C., was obtained.

EXAMPLE 7

The procedure of Example 1 was repeated, substituting tetraethylammoniumchloride on an equimolar basis for the hexaethylguanidinium chloride. Asimilar product, melting at 188-190° C., was obtained.

EXAMPLE 8

The procedure of Example 1 was repeated, substitutingtetra-n-butylammonium chloride on an equimolar basis for thehexaethylguanidinium chloride. A similar product, melting at 217-219°C., was obtained.

EXAMPLE 9

The procedure of Example 1 was repeated, substitutingtetra-n-butylphosphonium chloride on an equimolar basis for thehexaethylguanidinium chloride. A similar product, melting at 219-221°C., was obtained.

EXAMPLE 10

A 10-ml vial was charged with 440.5 mg (4 mmol) of hydroquinone, 160 mg(2 mmol) of a 50% aqueous sodium hydroxide solution and 3 ml ofmethanol. The vial was agitated until a homogeneous solution wasobtained. Catalyst solution containing 27.85% hexaethylguanidiniumchloride, in the amount of 2 mmol of the guanidinium salt, and 2 ml ofmethanol were added, with stirring. A precipitate of the desiredhexaethylguanidinium hydroquinone salt, as shown by proton nuclearmagnetic resonance spectroscopy, formed immediately and was collected byfiltration; the yield was 70% of theoretical.

EXAMPLE 11

A 10-ml vial was charged with 440.5 mg (4 mmol) of resorcinol, 160 mg (2mmol) of a 50% aqueous sodium hydroxide solution and 3 ml of methanol.The vial was agitated until a homogeneous solution was obtained.Catalyst solution containing 27.85% hexaethylguanidinium chloride, inthe amount of 2 mmol of the guanidinium salt, and 2 ml of methanol wereadded, with stirring. The resulting solution was cooled in an ice-waterbath, whereupon a fine flocculent precipitate of the desiredhexaethylguanidinium resorcinol salt, as shown by proton nuclearmagnetic resonance spectroscopy, gradually formed; it was collected byfiltration. The yield was 40% of theoretical.

EXAMPLE 12

A 416-l continuous stirred tank reactor was charged with 62.89 kg(275.47 moles) of bisphenol A and 70.00 kg of anhydrous methanol. Theresulting solution was heated to reflux and 11.15 kg (139.385 moles) of50% aqueous sodium hydroxide solution was added over 0.5 hour. To theresulting whitish slurry was added catalyst solution containing 27.85%hexaethylguanidinium chloride, in the amount of 40.711 kg of theguanidinium salt. After approximately 10-20% of the catalyst solutionhad been added, a noticeable fine white precipitate had formed. Afterthe addition was complete, an additional 85.90 kg of water was added.

The reaction mixture was allowed to cool from 65° C. to approximately18-20° C., during which time the guanidinium bisphenolate precipitatedas fine cubic crystals. The crude precipitate was collected byfilter-centrifugation and rinsed with 50 liters of water. After extendedcentrifugation, the crude yield of material was 105.5 kg. The productwas dried in a vacuum tumble dryer to yield 94.06 kg was obtained(99.84% of theoretical). Analysis by ion chromatography and protonnuclear magnetic resonance spectroscopy showed the product to be 99+%pure, containing 242 ppm residual sodium ion as sodium chloride.

The product was further purified by recrystallization frommethanol-water. A 416-l continuous stirred tank reactor was charged with40 kg of the product and the 252.84 l of methanol, and the solution wasbrought to reflux. Additional water (133.40 kg) was added. After about10-15% of this water had been added, a whitish precipitate formed. Thehot solution was allowed to cool to 15-18° C. and the product wascollected by filter-centrifugation. The crystalline material was rinsedwith 40 l of water. The recrystallization yielded 33.60 kg of thepurified hexaethylguanidinium bisphenolate. This material was driedunder vacuum in a tumble dryer for 48 hours. The final dry yield was32.17 kg (95.14% of theoretical). Proton nuclear magnetic resonancespectroscopy, capillary electrophoresis and ion chromatography showedthe product to be 99.9+% pure with a residual sodium ion content (assodium chloride) of 0.50 ppm.

The quaternary bisphenolates of the present invention may be used invarious aspects of polymer synthesis. For example, as previouslysuggested they are useful as intermediates for conversion by alkalinehydrolysis to phase transfer catalysts useful in two separate overallprocesses for polyetherimide production. The first is the reaction, in asubstantially non-polar solvent, of an alkali metal salt of adihydroxyaromatic compound with a halo- or nitro-substitutedN-alkylphthalimide to produce a bisimide, which may be converted to adianhydride which can in turn undergo reaction with a diamine to formthe polyetherimide. The second is the reaction under similar conditionsof said alkali metal salt with a chloro- or nitro-substitutedbis(etherphthalimide), which directly affords the polyetherimide.Typical catalyst proportions in this reaction are in the range of about0.5-10.0 milliequivalents per equivalent of substituted phthalimide.

Alkaline hydrolysis of the quaternary bisphenolate to the polyetherimidecatalyst species may be achieved by combining it with excess alkalimetal hydroxide, typically a 15-25% excess over the theoretical molarratio of base to bisphenolate of 3:1, followed by removal of water whichis conveniently done azeotropically by adding the aqueous phasegradually to refluxing toluene. The hydrolysis product may then beremoved by filtration and/or distillation.

The quaternary bisphenolates may also serve as intermediates in variousstages of purification and recycle of materials in polyetherimidepreparation. For example, suitable treatment of waste streams from thedisplacement reaction of an alkali metal salt of bisphenol A with ahalo- or nitro-substituted phthalimide, using a hexaalkylguanidiniumhalide as catalyst, can afford the corresponding quaternary bisphenolatewhich, upon acidification, yields a hexaalkylguanidinium halide or thelike and the free bisphenol, both of which may be recycled. Thequaternary bisphenolate may also serve as an intermediate inpurification of the corresponding bisphenol.

Other uses for the quaternary bisphenolates are as catalysts in anyreaction in which a phenoxide moiety serves as a catalytic agent. Anexemplary reaction of this type is the preparation of branchedpolycarbonates by equilibration. Said reaction is disclosed, forexample, in U.S. Pat. No. 5,021,521, the disclosure of which isincorporated by reference herein.

The quaternary bisphenolates of this invention have been found to beexcellent equilibration catalysts. The equilibration reaction takesplace when an intimate mixture of a linear or branched polycarbonate, apolyphenolic compound and a carbonate equilibration catalyst is heatedin the melt, as in a batch melt reactor or an extruder, at temperaturesin the range of about 250-350° C. for approximately 5-30 minutes.

The proportions of catalyst and branching agent are ordinarily about10-500 ppm by weight and about 0.1-2.0 mole percent based on structuralunits in the polycarbonate, respectively. The quaternary bisphenolatedecomposes during the reaction to an olefin, a bisphenol and therelatively volatile pentaalkylguanidine, resulting in the production ofa branched polycarbonate of high stability and low color. Variousaspects of this method of preparing branched polycarbonates aredisclosed and claimed in provisional application Ser. No. 60121,749 andcopending, commonly owned application Ser. No. [RD-25278].

The quaternary bisphenolates are also active as catalysts in meltpolycarbonate formation by the reaction of a dihydroxyaromatic compound,usually a bisphenol such as bisphenol A, with a diaryl carbonate such asdiphenyl carbonate. They may be used alone or in combination with othersuitable catalysts such as tetraalkylammonium hydroxides. Typicalproportions of the quaternary bisphenolate for this purpose, and alsofor any other catalyst additionally employed, are from about 0.2 moleppm to about 0.1 mole percent. The melt polycarbonate thus produced isfrequently found to have reduced levels of color bodies and branchedand/or crosslinked polymer in comparison to polycarbonates obtained withthe use of alkali or alkaline earth metal bases as catalysts.

The use of the quaternary bisphenolates as catalysts and catalystintermediates is illustrated by the following examples.

EXAMPLE 13

A 50-ml round-bottomed flask equipped with a reflux condenser, magneticstir bar and nitrogen purge means was charged with 7.36 g (10.7 mmol) ofthe product of Example 1, 15 ml of water and 3.01 g of 50% aqueoussodium hydroxide solution (37.5 mmol of sodium hydroxide). The mixturewas stirred under nitrogen at 100° C. to effect solution, and was thentransferred to a heated constant addition funnel and diluted with 15 mlof water. It was dripped into 200 ml of refluxing toluene in a 250-mlround-bottomed flask equipped with a stir bar, Dean-Stark trap toppedwith a reflux condenser and nitrogen purge means. All of the water wasremoved by distillation over approximately 20 minutes, after which 100ml of toluene was removed by distillation to yield a slurry of a whiteprecipitate in toluene, which was dried by vacuum stripping and heatingat 150° C. under reduced pressure.

A 250-ml, 2-necked round-bottomed flask fitted with a reflux condenser,a magnetic stir bar, a Dean-Stark trap and nitrogen purge means wascharged with 7.54 g (27.7 mmol) of anhydrous bisphenol A disodium saltand 85 ml of anhydrous toluene. The mixture was stirred and heated toremove 34 ml of toluene and any remaining moisture by azeotropicdistillation. A capped tube was charged with 11.42 g (55 mmol) of dried4-nitro-N-methylphthalimide and 410 mg of the above-prepared white solid(0.53 mmol of active catalyst) and the contents thereof were transferredto the toluene slurry. The mixture was heated under nitrogen at 145° C.,with stirring, for 90 minutes and was then cooled to 80° C. Uponsampling and analysis, it was determined that the desired2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane bis-N-methylimide hadbeen formed in 98.1% yield.

EXAMPLE 14

A dry blend was prepared from a commercial bisphenol A polycarbonatehaving a weight average molecular weight of about 66,000 relative topolystyrene as determined by gel permeation chromatography, the productof Example 1 as an equilibration catalyst in the amount of 129 ppm byweight and [1,1 -bis(p-hydroxyphenyl)ethyl]phenyl ether as a branchingagent, the latter compound having been prepared by Friedel-Craftsacylation of phenyl ether with acetic anhydride followed by reactionwith 4 moles of phenol in the presence of boron trifluoride-ethyl ethercomplex and 3-mercaptopropionic acid. The blend was extruded on a twinscrew extruder at a temperature of about 280° C., with vacuum venting.The product was the desired branched polycarbonate.

EXAMPLES 15-19

In these examples, a 1-l glass melt polymerization reactor was washedwith acid, rinsed and dried at 70° C. overnight to passivate thesurfaces thereof. It was charged with 137 g (600 mmol) of bisphenol A,135 g (630 mmol) of diphenyl carbonate and various catalytic amounts ofthe product of Example 1. A helixing stirrer was suspended in thepowdered mixture and the reactor was evacuated three times to 1 torr,followed each time by refilling with purified nitrogen.

The reactor was heated to 180° C., whereupon the mixture melted. It wasthermally equilibrated, with stirring, for 5-10 minutes. In Examples15-18, a catalytic amount of tetramethylammonium hydroxide was added atthis point. Stirring at 180° C. was continued for an additional 5minutes, after which the temperature was raised to 210° C. and thepressure lowered to 175 torr, whereupon phenol began to distill from thereactor.

After 35 minutes, the reactor pressure was lowered to 100 torr andstirring was continued for 35 minutes. The temperature was then raisedto 240° C. and the pressure reduced to 15 torr for 40 minutes, to 270°C. and 2 torr for 20 minutes, and to 300° C. and 0.62 torr for 75minutes.

The products were the desired polycarbonates. Catalyst details andproperties of the products are listed in the following table. Molecularweights were determined by gel permeation chromatography relative topolystyrene; catalyst amounts are based on bisphenol A.

    ______________________________________                                        Example   Catalyst         Mw      Mn                                         ______________________________________                                        15        Example 1, 250 mole ppm                                                                        33,700  12,300                                               TMAH, 83.3 mole ppm                                                 16        Example 1, 42 mole ppm                                                                         55,800  20,300                                               TMAH, 83.3 mole ppm                                                 17        Example 1, 0.42 mole ppm                                                                       33,500  12,400                                               TMAH, 83.3 mole ppm                                                 18        Example 1, 4.2 mole ppm                                                                        81,700  27,300                                               TMAH, 83.3 mole ppm                                                 19        Example 1, 0.42 mole ppm                                                                       43,200  19,400                                     ______________________________________                                    

What is claimed is:
 1. A method for preparing a polyether orintermediate therefor which comprises contacting, at a temperature inthe range of about 100-250° C., at least one alkali metal salt of adihydroxyaromatic compound with at least one halo- or nitro- substitutedaromatic compound in the presence of a catalytic amount of an alkalinehydrolysis product of a quarternary salt of a dihydroxyaromaticcompound, the salt having the molecular formula

    H.sub.3 Q(OA.sup.1 O).sub.2,                               (I)

wherein A¹ is a divalent aromatic radical and Q is a monocationiccarbon- and nitrogen- or phosphorous-containing moiety.
 2. A methodaccording to claim 1 wherein the dihydroxyaromatic compound is bisphenolA and the substituted aromatic compound is 4-nitro-N-methylphthalimide.3. A method according to claim 1 wherein the dihydroxyaromatic compoundis bisphenol A and the substituted aromatic compound is a chloro- ornitro-substituted bis(etherphthalimide).
 4. A method of preparing apolycarbonate which comprises equilibrating a reaction system comprisinga linear or branched polycarbonate in the presence of a catalytic amountof a quaternary salt of a dihydroxyaromatic compound, the salt havingthe molecular formula

    H.sub.3 Q(OA.sup.1 O).sub.2,                               (I)

wherein A¹ is a divalent aromatic radical and Q is a monocationiccarbon- and nitrogen- or phosphorous-containing moiety.
 5. A methodaccording to claim 4 wherein the reaction system also contains apolyphenolic compound as a branching agent.
 6. A method according toclaim 4 wherein the polycarbonate is a bisphenol A polycarbonate.
 7. Amethod of preparing a polycarbonate which comprises contacting at leastone dihydroxyaromatic compound with a diaryl carbonate In the melt inthe presence of a catalytic amount of a quaternary salt of adihydroxyaromatic compound, the salt having the molecular formula

    H.sub.3 Q(OA.sup.1 O).sub.2,                               (I)

wherein A¹ is a divalent aromatic radical and Q is a monocationiccarbon- and nitrogen- or phosphorous-containing moiety.
 8. A methodaccording to claim 7 wherein the polycarbonate is a bisphenol Apolycarbonate.